Typically, when a wiper blade wipes to wipe dirt from a vehicle window glass, a washing device supplies washer liquid to the surface to be wiped. For example, Japanese Laid-Open Utility Model Publication No. 54-180541 discloses a pipe having a rigidity that properly supplies washer liquid to a surface to be wiped. The rigid pipe attached to an wiper arm to extend along a wiper blade at an outer side of the wiper blade. The rigid pipe has a number of spray holes for spraying washer liquid to the surface to be wiped at close range.
However, in the above configuration, the rigid pipe with the spray holes are exposed to the outside of the wiper blade. Such piping spoils the appearance of the vehicle. Further, direct sunlight accelerates degradation of the pipe, and the spray holes can be blocked by snow, dust, or bird dropping. That is, there has been a demand for a structure that is capable of spraying (supplying) washer liquid to a surface to be wiped over an extended period of time.
Japanese Laid-Open Utility Model Publication No. 2-132566 discloses a wiper device in which washer nozzles are attached to a wiper blade and a wiper arm, so that washer liquid is reliably supplied to a surface to be wiped. The washer liquid is thus sprayed onto the surface to be wiped at close range. To supply washer liquid from a tank to the washer nozzles, hoses extend along the wiper blades and wiper arms.
However, in the prior art wiper devices, residual washer liquid in the hoses can leak from the wash nozzles in a standby state, where no washer liquid should be supplied to the surface to be wiped. Particularly, in the wiper device of Japanese Laid-Open Utility Model Publication No. 2-132566, the washer nozzles are attached to reciprocating members, or the wiper blades and wiper arms. In such a case, residual washer liquid in the hoses receives centrifugal force generated by pivoting motion of the wiper blades and wiper arms and concentrate at the washer nozzle. This is likely to cause the liquid to leak from the nozzles.
Washer liquid that has leaked from the washer nozzles can collect on the surface to be wiped prior to the wiping operation of the wiper blade. In this case, no problem is caused since the wiper blade wipes the leaked washer liquid right away. However, washer liquid that has leaked during a reverse motion of the wiper blade collects on a surface to be wiped immediately after the wiper blade has wiped that surface. Therefore, until the wiper blade wipes the surface in the subsequent cycle, the leaked washer liquid remains on the surface to be wiped, which can disturb the driver's view.
Also, if washer liquid leaks from the washer nozzles, the amount of washer liquid in the hoses is decreased. Therefore, in the subsequent spraying of the washer liquid, the spraying is not started until the hoses are filled with washer liquid. Accordingly, the responsiveness of the device is degraded. That is, the time from when the operation for supplying the washer liquid is performed to when the washer liquid is actually sprayed is extended.